Ed Miliband will do 'more damage to the country than he did to his brother', Boris Johnson said this morning as the pair clashed on live TV.

The London Mayor, who appeared alongside Mr Miliband on the BBC's Andrew Marr show, launched a furious personal assault on his rival as their encounter descended into a shouting match.

Mr Miliband appeared to laugh off the attack, responding: 'Come on Boris, you're better than that.'

Boris Johnson launches furious attack on Miliband live on TV

Boris Johnson, who appeared alongside Ed Miliband on the BBC's Andrew Marr show, launched a furious personal assault on his rival as their encounter descended into a shouting match

The Labour leader appeared to laugh off the attack, responding: 'Come on Boris, you're better than that'

Mr Johnson said Labour could not take power without the support of the SNP and claimed the prospect was 'actually deeply alarming'.

He said Mr Miliband would have to take help from the SNP 'crouching on his back like a monkey' - making it impossible for him to govern in the interests of the whole country.

The London Mayor said: 'I'm not saying your brother had to present himself... with a dagger in the back [but] he would do more damage to this country than he did to his brother, and that is the key point.'

Mr Miliband hit out at the Conservatives for their campaign, saying: 'They are so desperate they are reduced to trying to set one part of the country against another.'

Mr Johnson insisted the Conservative attacks on the SNP were not risking the union.

'I'm so proud and so positive about what's happening in this country at the moment and I just think there are unnecessary risks involved in this Labour-SNP condominium.

'[So the answer would be, no I don't think we are in any way imperilling the union. The people who would imperil the union, because that's what their party is called, is the Scottish Nationalist Party.

'And I imagine their strategy - like the parable, or the fable, of the frog and the scorpion - is to be allowed to be carried across the river and then ultimately to sting... [cut off]'

Mr Johnson said Labour could not take power without the support of the SNP and claimed the prospect was 'actually deeply alarming'

Mr Miliband was driven to the BBC studios in central London this morning, while the London Mayor cycled

The Conservatives have made the potential of a Labour administration reliant on SNP votes one of the central planks of their election campaign in the last two weeks.

But Mr Miliband repeatedly insisted he would not make any 'deals' with the SNP to become Prime Minister.

He said: 'No coalition, no tie-ins, I have said no deals; I have been clear about that,' he told the Andrew Marr Show.

'I am not doing deals with the Scottish Nationalist Party.'

Asked explicitly whether he was ruling out a confidence-and-supply agreement, he replied: 'No deals.'